Massive immature mediastinal teratoma extending into the left pleural cavity.

We report a case of a massive mediastinal teratoma in an 18-year-old woman who presented with a short history of exertional dyspnoea. The tumor arose from the left lobe of the thymus and extended into the left pleural cavity, completely compressing the left lung and extensively shifting the mediastinum to the right. Measuring 23 cm x 17 cm x 9 cm and weighing 2005 g it is one of the largest anterior mediastinal teratomas reported.